Control for variable displacement pumps



y 1949. w. M. HODDINOTT 2,470,617

CONTROL FOR VARIABLE DISPLACEMENT PUMPS Filed Aug. 28, 1944 2 Sheets-Sheet l 2 60 6 evil 3. 58 6 11 I K1 6 70 12 l Z/ INVENTOR mil/AM M. //000//V077' Ill .1: I I :ffifjfj: II. 4,5 BY 9 m/ ATTORNEYS May 17, 1949. w. M. HODDINOTT 2,470,517

I CONTROL FOR VARIABLE DISPLACEMENT PUMPS Filed Aug. 28, 1944 2 Sheets-Sheet 2 INVENTOR mum/w M HOBO/N0 77 Y 31 62%! ATTORNEYS Patented May 17, 1949 -GON-TROL FOR VAIRIABLE DISPLAGEMENT --'-PUMl-S --*William MFHoddindtt, Springfield, Massgfassigfior to van Norman Gompany,"springfieldg Masss a corporation ofi Massachusetts Application A'ugust'28, 1944; serial No. 551,466

(Cl-(M3 38) I 4Glaims.

"This invention relates tofi-mprovenirants in control mechanism" for variable delivery pumps, particularly "such 'as' "are" employed as variable speed driving meansformachine' tools. In some types of" machine tcoisysuenas milling machines, it is'neces'sary that the "driven-- member be capable er moving "at b'othdeed andrapid traverse rates in "both directions. ""In "prior constructions this has'been accomplished by the use Of a reversing valve or" by reversingthe direction of thepump, neither of'which are desirabie on account of the added mchariismrequired. It is the object of this-invention to"pro"d'uce=a unitary control for a uni-directional variable-delivery hydraulic pump,

in which a change from rapidtraverse to feed tati-ng shaft 2 drives a rotor 3 e'za'irrying pistons 4 1 extending i-nto-a-plural oylirfder member 5 rotat- *able into varieusangularpositions about I a pivot 6. "Pipes -8 connect the" cylinder member, -'as for example through its pivot, with a suitable hydraulic motor which may be of the cylinder and piston type but is here shown as a rotating hydraulic motor 9 of a type generally similar to that of the pump. This motor drives a shaft II] which may be connected directly to a screw shaft forming part of a table operating mechanism, but which is preferably coupled to said screw shaft through speed changing mechanism as will be described below. The pump I may be enclosed in an oil-flooded casing II to prevent loss of oil from the pump and provided with the usual means to insure that the entire system is flooded with oil at all times.

With the general type of pump shown, the direction of movement of the driven mechanism will be reversed by swinging the pivoted member 5 to one side or the other of its center, and its rate of movement controlled by the degree of displacement of that member. This degree of displacment is varied by shifting a rod l2 connected to a pin l3 on the member -5 by a link or by a 5: 2 slideway fl. rod slides-in bearings l5,i6 "in a housing I l "(Fig. '2) which contains the con- *trolfineclianism" proper. In order-to avoid the "necessity for accurate placing of the'housing, the rodr l; 2 is preferably"profidewwitha turn-buckle ""l'8. Tlierodi hasrach teeth' l9"whic-h mesh with along pinion'z c rotatably mounted in the housing '11. -"Al'so"engaging"with"the pinion *zmama on "oppositef'sidesof it areiack teeth-2 I,"22 o n' rod pistons" 23 '24 sliding snugly in---cylindrical holes '25, 26"-and-each'"'proiiecting atnneend into a chamber "21 within'" thehousing. This chamber actsas acylinderfora piston!!! having'its piston "r0d?e-eiitendingthrou'gha viallwinto meson-d chairibenB I an'dscrewthradedat 32. Threaded onto the rod 29 is a pinion 33 engagingaldng gear 34 journaled in the housing and having a "longs'liah'k -"ifi whichmay'be adjusted by a wrench or oth'er suitable means. When the--piston -Z8 "is *iorce'dupwardly byjhydraulic pressure as will be "ol'escribedfthe pinion-"33 will strike the upper -por- *tionof the chairibei 3 rattan/111- iimitthe upward "travel of he-pistoni accordance with the positionfofhe 'pi'ston onthe screw threads 32 as determ-ined byrotatingthe pinion by the shank 35. *Whn the piston des"cer'1ds-'-'in-the"absence 'ofhydraulic pressure underneath it itslimit of motio 'is' determ-ine'd by fits contact with wall 30. To --prevent rotation 6f theserewf threaded rod? 9' it isslottedeat 36 and held by a set-screw -3 1' 'clamped by a sec'o'n dset-screw 38.

39"an'd to a direction-"control --va1ve 4 lof cus- "tel-nary--type;= which *reeei'ves its pressure-fluid through piping 42 from a constant delivery pump 43 provided with a relief valve 44 for return of excess fluid to the sump 45 through a line 46. A line 41 extends from the valve 4| to the sump. As the spindle 4B of the valve spool is shifted in one direction or the other the plungers 23, 24 will be alternately pushed down by hydraulic pressure, the inactive plunger having the pressure chamber above it vented to the sump through line 41. The effect of the movement of the p1ungersone of which must go up as the other goes down on account of their mutual connection with pinion 2|Iis to shift the rod [2 in one direction or the other through a distance determined by the position of piston 28. If the piston is held up by hydraulic pressure the pump will be adjusted to feed rate, while if the piston is down the pump will be held in rapid traverse. The rapid traverse position may be the maximum eccentricity of the pump, while the feed position is determinable by adjustment of the shank 35.

To shift from rapid traverse to feed the chamber 21 below piston 28 is connected by a hydraulic line 49 to a conventional reversing valve 56, having a central connection through a pipe 5| with the pressure line 42 and end connections through a pipe 52 to the drainage line 41. In one position of the valve line 49 is connected to the pressure line, and in the other position to the sump. It is not necessary to provide a second hydraulic connection to move piston 28 downwardly, plungers 23 and 24 accomplishing this once pressure underneath the piston has been removed.

It is possible to increase the range between feed and rapid traverse still more by a change in gearing synchronized with the change in position of the pump. For this purpose the shaft l driven by the hydraulic motor 9 is provided with worms 54 and 55 meshing with worm wheels 56 and 51 respectively. The two worm and wheel combinations are made of different ratios, as by making 54, 56 a single and 55, 51 a quadruple thread. The wheel of the latter will thus be driven at a higher speed than wheel 56. Wheel 56 is loose on a cross shaft 58, while wheel 51 is coupled as by a chain belt 59 with a sleeve 69 also loose on the shaft. A clutch member 6| is fixed to rotate with the shaft but slidable upon it, so that it may be shifted as by a rocker 62 to cause the shaft 58 to be driven at a high rate through train 55, 51, 59 or at a lower rate through train 54, 56. The rocker 62 is actuated by a hydraulic servomotor 63 connected to the upper end ports of valve 50 by pipes 64, 65. As valve 58 is shifted to either feed or rapid traverse positions the clutch 6l will be correspondingly shifted.

I claim:

1. A hydraulic drive comprising a variable delivery pump adjustable on both sides of neutral to preset feed and rapid traverse positions, and means for adjusting the pump comprising a rod, a pair of plungers connected to the rod to move it in opposite directions, a single abutment positioned to limit said movement of both said plungers, and means to shift said abutment between positions giving respectively a long and a short travel to the plungers.

2. A hydraulic drive comprising a, variable delivery pump adjustable on both sides of neutral to preset feed and rapid traverse positions, and means for adjusting the pump comprising a rod, a pair of plungers connected to the rod to move it in opposite directions, a single abutment positioned to limit the movement of both said plungers, means to shift said abutment between positions iving respectively a long and a short travel to the plungers, and means for adjusting the second named position of the abutment independently of said shifting means.

3. A hydraulic drive comprising a variable delivery pump adjustable on both sides of neutral, and means for adjusting the pump comprising a rod, a pair of plungers connected to the rod to move it in opposite directions, a single abutment positioned to limit the movement of both said plungers, a threaded shank on said abutment, a stationary member through which the shank passes, means for holding the shank against rotation, a pinion threaded on the shank and adapted to contact the stationary member on the opposite side from the abutment, a long gear in constant mesh with the pinion, means to rotate the gear to change the position of the pinion on the shank, whereby the abutment may be shifted between positions determined respectively by contact of the abutment and contact of the pinion with said stationary member.

4. A hydraulic drive comprising a variable delivery pump adjustable on both sides of neutral to preset feed and rapid traverse positions, means for adjusting the pump, single means limiting the maximum adjustment of the pump in both directions, means for shifting said single means bodily to a position corresponding to a lesser pump delivery, and means independent of said shifting means for adjusting said latter position.

WILLIAM M. HODDINOTT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,385,289 Ward Nov. 16, 1917 1,573,525 Sandoz Feb. 16, 1926 1,785,355 Lawser Dec. 16, 1930 1,929,185 Ferris Oct. 3, 1933 2,113,161 Osborne Apr. 5, 1938 2,114,443 Foisy Apr. 19, 1938 2,140,633 Kooks Dec. 20, 1938 2,142,500 Douglas Jan. 3, 1939 2,146,133 Tweedale Feb. 7, 1939 2,155,455 Thoma Mar. 25, 1939 2,240,898 Weidmann May 6, 1941 2,275,758 Harris Mar. 10, 1942 2,303,955 Rose Dec. 1, 1942 

